The present invention relates to a control unit for a construction machine, and more particularly to an electronic control system for a construction machine which includes a plurality of control units for controlling a prime mover, hydraulic equipment, a working device, a display unit, etc., and which interconnects the plurality of control units via a common communication line for transmission and reception of data.
Recently, with the advancement of electronic control incorporated in construction machines, particularly in a hydraulic excavator as a typical example thereof, the amount of computation to be processed by a control unit has increased more and more because of various kinds of computation required for the electronic control. The increased amount of computation necessitates the use of a high-performance microcomputer, and hence pushes up a cost. Also, the number of input/output signals is increased, which results in an increased number of wire harnesses. To overcome such a problem, dispersion of control units has been studied. In dispersion of control units, control functions of a hydraulic excavator are divided in units of function, control units are provided one for each of the unit functions, and the control units are interconnected via a network for performing control.
For example, JP, B, 7-113854 discloses an electronic control system for a hydraulic excavator wherein control units are provided one for each device, the control units for the respective devices are connected to a master controller via a common communication line, and integration of the overall system is maintained by the master controller.
Also, JP, B, 8-28911 discloses an electronic control system for a construction machine wherein control units are provided one for each device, and the control units are interconnected via a multi-transfer serial communication circuit to construct a network capable of two-way communication. This system is easily expandable.
Further, SAE Paper 941796 Development of Intelligent Hydraulic Excavatorxe2x80x94HYPER GX Series (published in 1994) discloses an electronic control system for a hydraulic excavator wherein control units are provided one for each device, and the control units are interconnected via a network. The network is divided into a low-speed network and a high-speed network to ensure reliability of high-speed communication data and realize a cost reduction of the overall system.
In a hydraulic excavator as a typical example of construction machines, as mentioned above, electronic control has been advanced and various improvements have been achieved in points of control performance and production cost.
On the other hand, customer needs for hydraulic excavators have become diversified, for example, ranging from a demand for high-performance functions to a demand for an inexpensive machine.
In the electronic control system disclosed in JP, B, 7-113854, to satisfy the above customer needs, software of the master controller must be developed and changed, and the master controller must be replaced for each need. Moreover, with replacement of the master controller, software of the control unit provided for each device and connected to the master controller must be developed and changed, and the resultant software must be substituted for that of the existing control unit. Particularly, when high-performance functions are demanded, e.g., when automatic control functions such as operating area limitation and locus control are to be added to an excavating device of a hydraulic excavator, the kinds of software installed in the control units are increased. As a result, the number of steps for development and the development cost or management cost are increased.
On the contrary, when high-performance functions of a hydraulic excavator are not needed, software of the master controller and the control units must also be developed and changed correspondingly, and the resultant software must be substituted for the existing software. Therefore, the number of steps required for software development and the development cost are increased.
In the electronic control systems disclosed in JP, B, 8-28911 and SAE Paper 941796, the control units for the respective devices are interconnected via the network, and all signals to be transmitted and received among the control units can be transferred using the network. Accordingly, even when a number of signals are transmitted and received, it is not required to increase the number of signal lines. Also, even when a control unit having a new function is added to the system, there is no need of increasing the number of signal lines. Those electronic control systems are thus flexibly adaptable for system expansion.
In the case of adding a control unit for system expansion, there is no need of increasing the number of signal lines, but each control unit must be itself adapted for an increase in the number of signals (data) to be transmitted and received. In other words, the existing control units must be replaced and hence the cost is pushed up. Further, in the case of requiring not so high-performance functions and desiring to reduce the number of control units, each control unit must also be adapted for a decrease in the number of signals (data) to be transmitted and received. Such a case therefore similarly requires replacement of the existing control units. Further, in the case of replacing one of a plurality of control units by another unit upon change of a hydraulic system or a control system, if a particular one of the plurality of control units executes processing using a received signal and a control unit transmitting the received signal is replaced and excluded from the system, the particular control unit must also be replaced.
Additionally, when a multiplicity of control units transfer data among them via a network, the network would be too crowded to utilize necessary data on demand unless communication frequency is held at an optimum level. This results in a deterioration of the control performance of the control units.
A first object of the present invention is to provide an electronic control system and a control unit for a construction machine including a plurality of control units interconnected via a common communication line, wherein additional connection of a control unit to the common communication line and disconnection of any control unit from the common communication line can be performed without changing software in the existing control units and replacing the control units themselves, and system change including addition, exclusion and replacement of one ore more control units can be easily realized.
A second object of the present invention is to provide an electronic control system for a construction machine including a plurality of control units interconnected via a common communication line, wherein data communication frequency over a network is held at an optimum level and the control performance of the control units is avoided from deteriorating.
(1) To achieve the above first object, the present invention provides an electronic control system for a construction machine comprising a prime mover, a working device, and a hydraulic system for generating liquid pressure power by the prime mover and driving the working device, the construction machine further comprising a plurality of control units, the plurality of control units being interconnected via a common communication line to transmit and receive data, wherein at least one of the plurality of control units includes minimum processing means capable of executing least necessary processing by itself when no data is transmitted via the communication line.
With that feature of providing the minimum processing means in at least one control unit, in the case of reducing the number of control units, the least necessary processing can be performed by the minimum processing means even when no data is transmitted via the communication line. There is hence no need of changing software and replacing the control units. This also similarly applies to the case where a control unit transmitting the relevant data is excluded as a result of partial replacement of a plurality of control units. Further, by designing software of the control units in anticipation of expansion of the system beforehand, need of changing software and replacing the control units can also be eliminated even for addition of a control unit. Therefore, one or more control units can be additionally connected to the common communication line or can be disconnected from the common communication line without changing software in the existing control units or replacing the control units themselves. It is hence possible to easily realize system change including addition, exclusion and replacement of one or more control units, and to hold down an increase of the development cost.
(2) Also, to achieve the above first object, the present invention provides an electronic control system for a construction machine comprising a prime mover, a working device, a hydraulic pump rotationally driven by the prime mover, actuators for driving the working device, control valves for controlling a hydraulic fluid supplied from the hydraulic pump to the actuators, and operating means for operating the control valves, the construction machine further comprising a plurality of control units, the plurality of control units being interconnected via a common communication line to transmit and receive data, wherein at least one of the plurality of control units includes minimum processing means capable of executing least necessary processing by itself when no data is transmitted via the communication line.
With that feature of dividing a control unit for a construction machine into a plurality of control units and interconnecting the plurality of control units via a common communication line to transmit and receive data, it is only required to modify, add or exclude the control unit at the least necessary level when manufacturing machines having different customer-demanded functions. Therefore, a system can be changed with the least necessary development cost and the least necessary number of development steps. Also, since the control units are divided for each function, the system is more convenient from the viewpoint of management and the management cost can be reduced.
In addition, with the feature of providing the minimum processing means in at least one control unit, as described in above (1), when one or more control units are added, excluded or replaced, there is no need of changing software and replacing the other control units. Thus, system change including addition, exclusion and replacement of one or more control units can be easily realized.
(3) In above (2), preferably, the plurality of control units include at least two of a control unit for controlling the prime mover, a control unit for controlling the working device, a control unit for controlling the hydraulic pump, a control unit for operating the control valves through the operating means, and a control unit for performing display and/or input in relation to the control units.
With that feature, system change including addition, exclusion and replacement of one or more control units can be easily realized, as described in above (2), for the control unit for controlling the prime mover, the control unit for controlling the working device, the control unit for controlling the hydraulic pump, the control unit for operating the control valves through the operating means, and the control unit for performing display and/or input in relation to the control units.
(4) In above (1) or (2), preferably, the minimum processing means has an initial value set therein for each data to be received via the communication line for fulfilling the least necessary function of each control unit, and performs computational processing by using the initial value when no data is transmitted via the communication line.
With that feature, when no data is transmitted via the communication line, the minimum processing means performs computational processing by using the initial value, and therefore the control unit can execute the least necessary processing by itself.
(5) Further, to achieve the above second object, in the electronic control system of above (1) or (2) according to the present invention, the plurality of control units each have an optimum transmission time interval set therein for each data to be transmitted to another control unit via the communication line, and transmits the data at the set time interval.
With that feature of setting an optimum transmission time interval for each data to be transmitted on the transmitting side and transmitting the data at the set time interval, the control unit can transmit data depending on a varying speed of the data or the cycle required for the control unit on the receiving side, and the amount of data flowing over the common communication line can be minimized within the necessary range. As a result, the common communication line can be utilized efficiently and the control performance is avoided from being affected by a lowering of the communication efficiency. In addition, even with an increase in the number of control units, the system is less susceptible to such a trouble as disabling communication due to excessive traffic on the common communication line.
(6) In above (5), preferably, the transmission time interval preset for each data to be transmitted is set depending a varying speed of the data or the cycle required for the control unit receiving the data.
With that feature, as described in above (5), the amount of data flowing over the common communication line can be minimized within the necessary range, and the common communication line can be utilized efficiently.
(7) In above (1) or (2) or (5), preferably, the plurality of control units each set a specific ID for each data to be transmitted or received via the communication line, and each have include communication means for transmitting data, which is to be transmitted via the communication line, with a specific ID assigned thereto, and for receiving only necessary item of data received via the communication line by identifying the necessary data based on a specific ID assigned thereto.
With that feature, in spite of various data flowing over the common communication line, each control unit can receive only necessary data. Further, each control unit can receive necessary information at a cycle required from the control point of view in a combination with the above feature (5), and hence the control performance is avoided from being affected by a lowering of the communication efficiency.
(8) Also, to achieve the above first object, the present invention provides a control unit for a construction machine comprising a prime mover, a working device, and a hydraulic system for generating liquid pressure power by the prime mover and driving the working device, the control unit being provided in the construction machine and connected to another control unit via a common communication line to transmit and receive data, wherein the control unit includes minimum processing means capable of executing least necessary processing by itself when no data is transmitted via the communication line.
With that feature, as described in above (1), when one or more of the control units provided in the construction machine are added, excluded or replaced, there is no need of changing software and replacing the other control units. Thus, system change including addition, exclusion and replacement of one or more control units can be easily realized.
(9) In above (8), preferably, the minimum processing means has an initial value set therein for each data to be received via the communication line, and performs computational processing by using the initial value when no data is transmitted via the communication line.
With that feature, as described in above (4), the minimum processing means performs computational processing by using the initial value, and therefore the control unit can execute the least necessary processing by itself.
(10) Further, to achieve the above first object, the present invention provides an electronic control system for a construction machine comprising a prime mover, a working device, and a hydraulic system for generating liquid pressure power by the prime mover and driving the working device, the construction machine further comprising a plurality of control units, the plurality of control units being interconnected via a common communication line to transmit and receive data, wherein at least one of the plurality of control units comprises first processing means for performing computational processing without using data transmitted from another control unit, second processing means for performing computational processing by using data transmitted from the another control unit, detecting means for detecting whether or not the another control unit is connected to the common communication line, and processing changeover means for executing the computational processing in the first processing means when connection of the another control unit is not detected by the detecting means, and for executing the computational processing in the second processing means when connection of the another control unit is detected by the detecting means.
With that feature of providing the first processing means, the second processing means, the detecting means and the processing changeover means in at least one control unit, when another control unit is connected to the common communication line, this fact is detected by the detecting means and the processing changeover means executes the computational processing in the second processing means. Also, when another control unit is disconnected from the common communication line, this fact is detected by the detecting means and the processing changeover means executes the computational processing in the first processing means. Therefore, one or more control units can be disconnected from the common communication line or displaced without changing software in the existing control units or replacing the control units themselves.
On the other hand, when another control unit is not connected to the common communication line, this fact is detected by the detecting means and the processing changeover means executes the computational processing in the first processing means. Also, when another control unit is additionally connected to the common communication line to increase the number of control units, this fact is detected by the detecting means and the processing changeover means executes the computational processing in the second processing means. Therefore, one or more control units can be additionally connected to the common communication line without changing software in the existing control units or replacing the control units themselves.
Thus, additional connection of a control unit to the common communication line and disconnection of any control unit from the common communication line can be performed without changing software in the existing control units and replacing the control units themselves. As a result, system change including addition, exclusion and replacement of one or more control units can be easily realized, and an increase of the development cost can be held down.
(11) Still further, to achieve the above first object, the present invention provides an electronic control system for a construction machine comprising a prime mover, a working device, a hydraulic pump, actuators for driving the working device, control valves for controlling a hydraulic fluid supplied from the hydraulic pump to the actuators, and operating means for operating the control valves, the construction machine further comprising a plurality of control units, the plurality of control units being interconnected via a common communication line to transmit and receive data, wherein at least one of the plurality of control units comprises first processing means for performing computational processing without using data transmitted from another control unit, second processing means for performing computational processing by using data transmitted from the another control unit, detecting means for detecting whether or not the another control unit is connected to the common communication line, and processing changeover means for executing the computational processing in the first processing means when connection of the another control unit is not detected by the detecting means, and for executing the computational processing in the second processing means when connection of the another control unit is detected by the detecting means.
With that feature of dividing a control unit for a construction machine into a plurality of control units and interconnecting the plurality of control units via a common communication line to transmit and receive data, it is only required to modify, add or exclude the control unit at the least necessary level when manufacturing machines having different customer-demanded functions. Therefore, a system can be changed with the least necessary development cost and the least necessary number of development steps. Also, since the control units are divided for each function, the system is more convenient from the viewpoint of management and the management cost can be reduced.
In addition, with the feature of providing the first processing means, the second processing means, the detecting means and the processing changeover means in at least one control unit, as described in above (10), system change including addition, exclusion and replacement of one or more control units can be easily realized.
(12) In above (11), preferably, the plurality of control units include at least two of a control unit for controlling the prime mover, a control unit for controlling the working device, a control unit for controlling the hydraulic pump, a control unit for operating the control valves through the operating means, and a control unit for performing display and/or input in relation to the control units.
With that feature, system change including addition, exclusion and replacement of one or more control units can be easily realized, as described in above (11), for the control unit for controlling the prime mover, the control unit for controlling the working device, the control unit for controlling the hydraulic pump, the control unit for operating the control valves through the operating means, and the control unit for performing display and/or input in relation to the control units.
(13) In above (10) or (11), preferably, the detecting means detects whether or not the another control unit is connected, depending on whether or not data is received from the another control unit.
With that feature, whether or not another control unit is connected can be detected by software processing.
(14) In above (10) or (11), preferably, the detecting means changes the status of a flag depending on whether for not data is received from the another control unit, and the processing changeover means determines based on the status of the flag whether or not the another control unit is connected, and changes over the computational processing to be executed.
With that feature, whether or not another control unit is connected can be detected by software processing, and the computational processing to be executed can be changed over.
(15) In above (10) or (11), preferably, the another control unit exists in plural number, each data transmitted from the plurality of other control units is assigned with a specific identifiers, and the detecting means detects whether or not the plurality of other control units are connected, depending on whether or not data is received from the plurality of other control units, and also detects based on the identifier of received data which one of the plurality of other control units is connected.
With that feature, even in the case where the another control unit exists in plural number and the second processing means performs computational processing by using data transmitted from the plurality of other control units, the detecting means can detect whether the plurality of control units are connected for each control unit, the processing changeover means can appropriately change over the computational processing, and the second processing means can execute the appropriate computational processing.
(16) Still further, to achieve the above first object, the present invention provides a control unit for a construction machine comprising a prime mover, a working device, and a hydraulic system for generating liquid pressure power by the prime mover and driving the working device, the control unit being provided in the construction machine and connected to another control unit via a common communication line to transmit and receive data, wherein the control unit comprises first processing means for performing computational processing without using the transmitted data, second processing means for performing computational processing by using the transmitted data, detecting means for detecting whether or not the another control unit is connected to the common communication line, and processing changeover means for executing the computational processing in the first processing means when connection of the another control unit is not detected by the detecting means, and for executing the computational processing in the second processing means when connection of the another control unit is detected by the detecting means.
With that feature, as described in above (10), when one or more of the control units provided in the construction machine are added, excluded or replaced, there is no need of changing software and replacing the other control units. Thus, system change including addition, exclusion and replacement of one or more control units can be easily realized.
(17) In above (16), preferably, the detecting means detects whether or not the another control unit is connected, depending on whether or not data is received from the another control unit.
With that feature, as described in above (13), whether or not another control unit is connected can be detected by software processing.